The effect of selective REM-sleep deprivation on the consolidation and affective evaluation of emotional memories

Emotion boosts the consolidation of events in the declarative memory system. Rapid eye movement (REM) sleep is believed to foster the memory consolidation of emotional events. On the other hand, REM sleep is assumed to reduce the emotional tone of the memory. Here, we investigated the effect of selective REM-sleep deprivation, SWS deprivation, or wake on the affective evaluation and consolidation of emotional and neutral pictures. Prior to an 9-h retention interval, sixty-two healthy participants (23.5 ± 2.5 years, 32 female, 30 male) learned and rated their affect to 80 neutral and 80 emotionally negative pictures. Despite rigorous deprivation of REM sleep or SWS, the residual sleep fostered the consolidation of neutral and negative pictures. Furthermore, emotional arousal helped to memorize the pictures. The better consolidation of negative pictures compared to neutral ones was most pronounced in the SWS-deprived group where a normal amount of REM sleep was present. This emotional memory bias correlated with REM sleep only in the SWS-deprived group. Furthermore, emotional arousal to the pictures decreased over time, but neither sleep nor wake had any differential effect. Neither the comparison of the affective ratings (arousal, valence) during encoding and recognition, nor the affective ratings of the recognized targets and rejected distractors supported the hypothesis that REM sleep dampens the emotional reaction to remembered stimuli. The data suggest that REM sleep fosters the consolidation of emotional memories but has no effect on the affective evaluation of the remembered contents.